1. Field of the Invention
The present invention relates generally to semiconductor detectors, and, more specifically, to photo-sensitive detectors.
2. Description of Related Art
Detection and imaging systems capable of operating in the long wavelength infrared (LWIR) range are used in, for example, space surveillance systems. For the purposes of the present application, the term LWIR is intended to mean those wavelengths considerably in excess of 1 .mu.m, typically on the order of 10 to 15 .mu.m and extending to nearly 30 .mu.m.
These LWIR systems impose critical performance limitations on such parameters as resolution, field-of-view, operating temperature, responsivity, detectivity, ease of calibration, and radiation hardness.
Detectors based on impurity band conduction (IBC detectors), also known as Blocked Impurity Band (BIB) detectors, have been disclosed in, e.g., U.S. Pat. Nos. 4,568,960, 4,586,074, 4,586,068, and 4,313,127. These detectors are useful in the LWIR range required and typically comprise an active layer which is doped with a sufficient amount of either a donor or an acceptor impurity such that significant charge transport can occur in an impurity band in addition to the charge transport of electrons in the conduction band of the active layer and of holes in the valence band of the active layer. A blocking layer is disposed on the active layer and contains a sufficiently low concentration of impurities that significant charge transport cannot occur in the blocking layer except by means of electrons in the conduction band of the blocking layer and by means of holes in the valence band of the blocking layer. Conventional IBC detectors can be operated in a gain mode. However, a disadvantage of the IBC detector in gain-mode is significant gain dispersion noise.
Thus, improvement in the performance of gain-mode IBC detectors is needed.